Composite friction elements and pultrusion method of making same

ABSTRACT

A composite friction unit of a three dimensional composite body is formed of a substantially uniform array of predominately glass strands of primary reinforcing fibers in matrix of phenolic resin material, the reinforcing fibers in the form of fabric distributed throughout the body forming a friction unit having a predetermined size and configuration and uniform distribution and alignment of fibers throughout. An alternate friction unit includes a substantially rigid or rigid backing co-pultruded in forming the unit. The units are produced in a pultrusion process wherein the reinforcing fibers and matrix are pulled through a forming die.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of earlier U.S. patentapplication Ser. No. 12/841,657, filed Jul. 22, 2012, which applicationis a continuation-in-part application of earlier U.S. patent applicationSer. No. 10/164,191, filed Jun. 5, 2002, the disclosures of which arehereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to composite friction elements for brakesand clutches and pertains particularly to improved friction elements,composition and method for making same.

A friction brake is basically a pair of friction members, one rotatingand one stationary, brought into engagement to produce a friction forcemeasured as brake torque for either slowing or stopping the rotatingelement. Brakes are preferably designed so that the brake torque issomewhat proportional to the input force used to engage the elements andthe energy of the rotating member is dissipated in the form of heat.Unfortunately, pressure is not the only factor that influences thefrictional response of the brake elements. Friction effects betweenfriction elements cause friction force and brake torque to vary withengaging pressure, speed, and temperature, and to depend upon depositedinterfacial film for stability. Nevertheless, brakes are preferablydesigned so that the brake torque is reasonably proportional to theinput force used to engage the elements. The energy of braking isdissipated in the form of heat through the brake elements. For thisreason they must be able to withstand a great deal of heat for mostapplications.

The rotating element of a brake system is usually a disc or drum made ofmetal such as a steel, and the stationary element is usually acomposition pad or shoe lining moveable into and out of engagement withthe rotating element. The composition element is designed to wearwithout undue wear of the metal disc or drum. The materials forming thecomposition element are the principle unpredictable variables that havethe greatest affect on the performance characteristics of the brakesystem. Desirable materials for the composition element must be safe touse, relatively inexpensive, have good friction, wear and heatperformance characteristics. This includes good fade resistance, or theability to maintain good (preferably substantially uniform) braking withheat buildup.

A friction clutch is similar in some respects to a brake and isbasically a pair of friction elements designed to selectively couple arotating driving element to a driven element to bring the driven elementup to speed to rotate with the driving element. The clutch elements,both rotating with one driving and one driven, are brought intoengagement to produce a friction force driving torque for bringingeither a slow moving or a stationary element up to speed with a rotatingdriving element. The clutch usually consists of a circular frictionplate or disc having friction pads or elements of composition materialon both faces squeezed between a pair of metal pressure plates.

Until recent years, the predominant reinforcing material used in themanufacture of friction pads and discs for brakes, clutches and the likewas asbestos. These pads were manufactured by a molding process whereeach unit was formed of a composition of randomly oriented asbestosfibers in a bonding matrix placed under pressure in a mold cavity.However, it was discovered that asbestos is a carcinogenic substance,and that such use released potentially harmful amounts of it into theenvironment. For this reason, some industrialized countries prohibit theuse of asbestos friction materials, and others including the UnitedStates require the use of asbestos to be phased out over the next fewyears. Therefore, there exists an urgent need for safe and effectivefriction materials and economical methods of manufacturing the materialsinto suitable friction units.

Extensive efforts have been put forth in recent years in an effort tofind suitable environmentally safe materials and compositions having thedesirable wear, heat and other characteristics to serve as a substitutefor asbestos as friction elements in brakes and clutches. These effortshave been frustrated by the many and varied parameters involved,including the range of needs to be met between brakes and clutches aswell as different types of brakes and different types of clutches. Forexample, different size vehicles require different size friction padsfor both brakes and clutches and often have other variables includinghigher operating forces and temperatures. Brake pads used with rotatingdiscs have different conditions than shoes used with brake drums. Alsoclutches used with automatic transmissions have different conditionsfrom clutches used with manual or stick shift transmissions.

Attempts to satisfy the need for long life, high friction heat resistantfriction materials have included proposals to utilize various choppedfibers molded in a bonding matrix, such as a resin. The friction unit isformed in the traditional fashion by a molding process, with the fibersand other components randomly oriented and placed in a binder, such aseither a dry powder resin cured under heat and pressure, or placed in aliquid resin in a mold and cured. Examples of these compositions andmanufacturing methods are disclosed in U.S. Pat. No. 4,119,591, grantedOct. 10, 1978 to Aldrich, U.S. Pat. No. 4,259,397, granted Mar. 31, 1981to Saito et al., and U.S. Pat. No. 4,432,922, granted Feb. 21, 1984 toKaufman et al.

However, friction units made by this method are expensive to manufactureand have not been satisfactory, because of their lack of uniformity inperformance and durability. For example, units from the same batch mayvary as much as 35% in performance characteristics. The non-uniformityof results has been found to be caused largely by a non-uniformity ofdistribution and orientation of the fiber and other components in thematrix. This not only creates expensive inspection and quality controlproblems, it can also create maintenance problems, and sometimes evenhazardous conditions. For example, pads that have been matched forperformance at initial installation may vary over their useful life.

Throughout the past several years, the applicant has developed extensiveimprovements in compositions and structures as well as in pultrusionmethods of manufacture of composite friction elements for brakes andclutches. Many of these improvements are embodied in the applicants U.S.Pat. No. 5,156,787, entitled “PULTRUSION METHOD OF MAKING BRAKELININGS”; U.S. Pat. No. 5,462,620, entitled “CONTINUOUS PULTRUSIONMETHOD OF MAKING FRICTION UNITS”; U.S. Pat. No. 5,495,922, entitled“UNIFORM COMPOSITE FRICTION UNITS; and U.S. Pat. No. 5,690,770 entitled“PULTRUSION METHOD OF MAKING COMPOSITE FRICTION UNITS. However, theapplicant's continuous work on perfecting these compositions, structuresand methods indicate that further improvements in both compositions andmethods of manufacture are desirable and consequently have beendeveloped by the applicant. For example, improved mechanical properties,compositions and structures were developed as well as improvements inpultrusion manufacturing methods.

Now then, further improvements are desirable in compositions, structuresand methods of manufacture. Accordingly, it is desirable that improvedcompositions, structures and methods of manufacture be available toovercome the above and other problems of the prior art.

SUMMARY OF THE INVENTION

It is the primary object of the present invention to provide improvedcompositions, structures and methods of manufacturing friction liningsfor brakes and clutches of all types. Another object of the presentinvention is to provide improved pultrusion process for the manufactureof friction linings for brakes and clutches. Another object is toprovide a means for co-manufacturing friction units with backingstructure by single process.

In accordance with a primary aspect of the present invention, frictionunits are manufactured by a pultrusion process and comprise acomposition of a controlled density and orientation of an array ofprimary reinforcing fibers in a phenolic resin with selected minorquantities of one or more of organic and inorganic friction modifiers.

Another aspect of the invention includes friction units made by acontinuous process comprising the steps of selecting a uniform array ofprimary strands of reinforcing fibers impregnated with a phenolic resinmaterial into which certain friction modifiers and process agents havebeen mixed, pulling the impregnated strands of reinforcing fibersthrough a composite forming die for forming a body having at least aportion of the three dimensional configuration of the friction units,and selectively cutting the body into a plurality of the friction units.

Another aspect of the invention includes friction units made by acontinuous process comprising the steps pulling the impregnated strandsof reinforcing fibers through a composite forming die together with apanel of a secondary material in a co-process to provide for an integralbacking or reinforcement portion to the friction unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the present invention willbecome apparent from the following description when read in conjunctionwith the accompanying drawings wherein:

FIG. 1 is a perspective view schematically illustrating an apparatus anda preferred method of carrying out the invention;

FIG. 2 is a view like FIG. 1 illustrating the method of making clutchlinings in accordance with the invention;

FIG. 3 is a perspective view of a typical woven panel of reinforcingfibers in accordance with the invention;

FIG. 4 is a view like FIG. 3 illustrating the woven panel of FIG. 3following a needling treatment for carrying out a step of a preferredmethod of the invention.

FIG. 5 is an elevation view illustrating a needling of multiple panelsof reinforcing panels;

FIG. 6 is an elevation view illustrating a needle for use in theoperation of FIG. 5;

FIG. 7 a view like FIG. 3 illustrating an alternate embodiment of awoven panel for carrying out a preferred method of the invention;

FIG. 8 is a plan view of a typical stitched panel of reinforcing fibersin accordance with the invention and

FIG. 9 is a plan view of a typical braded panel of reinforcing fibers inaccordance with the invention.

FIG. 10 is a perspective view schematically illustrating an apparatusand a preferred method of including a secondary material to provide anintegral backing or reinforcement portion toward carrying out theinvention.

FIG. 11 is a perspective view illustrating one product produced inaccordance with the invention.

FIG. 12 is a perspective view illustrating another product produced inaccordance with the invention.

DETAILED DESCRIPTION

The present invention is directed to improvements in a process known aspultrusion for the production of articles from composite materials. Thepultrusion process is a process wherein products or articles are formedin a die by pulling the materials through the die where they are shapedas to at least one significant dimension or configuration in theprocess. This distinguishes over the extrusion process wherein materialsare forced or pushed through a die under pressure and alternativeprocesses whereby products are molded individually in pressure cavitydies.

Referring to FIG. 1 of the drawing, there is schematically illustratedan exemplary system for carrying out an exemplary series of steps ofproducing linings for brakes and clutches in accordance with theinvention. The system, designated generally by the numeral 10, comprisessource of reinforcing fiber or fabric such as one or more spools orrolls 12 from which a panel 14 of a plurality of strands of an elongatedcontinuous fiber or arrays of fiber are drawn. The panels or arrays offibers are impregnated with a suitable resin such as by being passedthrough suitable injection chamber or wetting bath 16 of a suitableresin such as a phenolic resin and through a forming die 18 from which acomposite panel 20 emerges.

The panels of reinforcing fibers are pulled through the die 18 bysuitable pulling or traction means 22 such as a roller traction deviceas illustrated. The illustrated traction device comprises a pair ofrollers 24 and 26 between which the panel 20 passes and is gripped itand is pulled through the die. The rollers may be driven by a suitablemotor 28 which may be powered by any suitable means such as electric,air, hydraulic and other suitable power means. Other types of tractiondevices such as air or hydraulic powered reciprocating pulling grippersor tractors (not shown) may also be used. After the panel has emergedfrom the die the desired shape parts are cut from it by any suitablecutting means 30 such as a water jet, abrasive cutter, laser, plasma,stamping or other means.

As illustrated in FIG. 1, the emerging panel 20 is cut into brake padsof suitable, such as, an arcuate configuration. This cutting may beaccomplished by any suitable cutting means such as a water jet, abrasivecutter, laser, plasma, stamping or other means. The cutting process willdepend to an extent on the thickness and content of the material.Relatively thin materials, such as for small brake pads and clutchplates, may be cut by stamping with a die cutter or other suitablemeans. Certain clutch plates and abrasive discs for various applicationsmay be as thin as a single layer of woven reinforcing fibers. Thickermaterials such as for heavy duty brake pads and shoes will require othercutting means such as water jet or the like.

As illustrated in FIG. 2, the emerging panel 20 may be cut into clutchpads or discs of a ring or annular configuration. This cutting may beaccomplished by means of a die cutter 36 powered by an air or hydrauliccylinder 38. Because the materials are relatively thin such as forclutch plates, they can be easily cut by stamping with a die cutter.Clutch plates for some applications such as in automatic transmissionsmaybe as thin as a single layer of woven reinforcing fibers and mayinclude an integral backing or reinforcement portion.

The combination of fibers and resin are shaped at least as to certaindimensions and configurations of portions of the articles in the die andcured by heat prior to emerging from the die. In the illustratedembodiment, a generally flat rectangular panel 20 is formed from whichbrake or clutch pads 32 are cut or stamped. This is a continuous processforming at least some portions and dimensions such as the thickness andfriction surface of an article of manufacture. The fibers may be in theform of individual strands, woven fabrics, matting, or stitched fabricsor combinations of them. However, a preferred form of the reinforcingfibers is in a woven panel or matting wherein the primary fibers are inthe machine direction and cross woven fibers are at right angles to theprimary fibers or strands. The cross fibers may in some cases bealternately in other than ninety degrees (90) to the primary fibers.

Referring to FIG. 3, an exemplary preferred reinforcing panel isillustrated and designated generally by the numeral 40. The panel isshown as a traditional weave of fibers 42 which may be primary fibersextending in the machine or pull direction. Cross fibers 44 which may beconsidered secondary fibers extend substantially ninety degrees acrossthe fibers 42 in a traditional weave. The illustrated fibers 42 and 44may be a single strand or fiber or may be a string of multiple fibers ofthe same or different kind. The primary reinforcing fibers 42 and 44 forthe brake pads or linings are preferably glass fiber, but the pad maycontain other materials and fibers or combinations thereof. In addition,other fibers may be woven or distributed in with the glass fibers invarious selected distributions and proportions to alter and or enhancecertain characteristics. For example, various fibers may be distributedin various concentrations substantially uniformly throughout the unitfor optimizing various parameters such as inner laminar shear strength,wear, fade, and cooling. The addition of secondary reinforcing fiberscan be accomplished in several different ways.

Many different fibers or strands and combinations may be utilized,including but not limited to glass, rock, ceramic, carbon, graphite,aramid, nomex kevlar, wool and cotton fibers of other organic andinorganic materials. Various metallic fibers such as copper andaluminum, may also be utilized in various proportions with non-metallicfibers. In one preferred composition, the fibers amount to are about 20%to 60% by weight. Optic fibers may also be included in order to provideactive test and performance monitoring of the finished parts forevaluation or end use purposes.

The manufacturing system and process, as illustrated, provides for thecontrolled predetermined orientation of the primary fibers, as well asthe controlled predetermined uniformity and density of the primaryfibers within the resin matrix. For example, the composition of thefriction device determines many of its characteristics, such as itsdurability, heat resistance, and friction resistance. With this process,the primary fibers may be controllably distributed and orienteduniformly at any suitable angle to the friction surface of the brake pador friction device. Thus, the process and materials have the capabilityof providing superior, predictable and consistent performance.

The process may include the addition of secondary fibers that extendtransverse to the primary fibers in order to add shear strength andother mechanical properties to the units. In one form of the process, as

The panels 16 of fibers or strands are coated or wetted by a resin inany suitable manner either prior to (pre-preg) or during the pultrusionprocess. In the illustrated embodiment the fibers are shown to pass intoor through a bath or injector chamber 16 of a suitable liquid resincontained within a reservoir 20 for wetting or impregnating the fibersor strands. The fibers can also be impregnated with resin prior toprocess (pre-preg) or they may be wetted by resin injection or othersuitable means during the pultrusion process or as by drawing themthrough a bath or by pumping resin into them from a header thatsurrounds the rovings or panels of fibers. The fibers will in realitynumber in the hundreds or thousands, preferably in a matting of fibersin several rows many of which may be parallel and stitched together orinterleaved with other layers of different orientation. In theillustrated preferred system, the fibers are in the form of woven panelsor mats formed or cut to the width of the die and guided through intothe die 18 for imparting at least a part of the final shape orconfiguration of the friction units.

The strands, particularly if glass fibers, may require a sizingtreatment, i.e. application of a compound or chemical to insure a goodor complete wetting of the fibers and a good bond between the fibers andmatrix and between layers of fibers. A bulked roving (bunch of strandsor fibers) is preferably used. Bulked roving is produced by a process inwhich a standard roving is fractured or splintered by forced cold air.This provides two useful properties, 1) increased diameter which assistsin providing fill to low glass content pultrusion, and 2) the“splinters” provide for good mechanical bonding in all axis within theresin matrix.

The resin impregnated or wetted panels of fibers are passed or pulledthrough the die 18, where they are shaped into at least part of thedesired configuration and are at least partially, if not fully, cured.The fiber and resin composition is preferably at least partially curedin the die by any suitable means such as exothermic or radiant heat orother means, and the fibers will thereby be put in and remain in tensionin the body of the unit. The composite unit emerges, or moreparticularly is pulled in tension from the die in the form of anelongated continuous bar or panel 20 having at least part of theperipheral configuration of the brake or clutch pad or other articlebeing manufactured. In the case of brake and clutch pads, the bar orpanel preferably has the friction and mounting surface configuration ofthe final pad. The bar or panel 20 is pulled from the die 18 by suitablemeans, such as hydraulic pullers, tractors (not shown) or the like, andpositioned to be cut into individual friction or brake pad units orpieces in the illustrated embodiment. The pultrusion process provides asubstantially controlled composition with predetermined distribution andorientation of the primary fibers throughout the body of the frictionunit. This helps in maintaining a high degree of uniformity among theunits as well as in the various parameters of the units and their endperformance.

It may be desirable in some instances to provide a different angularityto the fibers in relation to the friction surface. For example, it maybe desirable to have the fibers at an angle to the friction surface ofup to as much as forty five degrees. This can be accomplished by cuttingthe friction units from the bar at the desired angle to the axisthereof.

The brake pads, upon being cut from the panel, may be placed on aconveyer belt or otherwise moved into position for further processingsuch as attachment to a backing plate. The pads or linings may beattached such as adhesively bonded to a backing plate or shoe. The padsare then accumulated by suitable manner in a suitable storage containeror bin where they are then packaged and shipped. This provides a highlyefficient and economical manufacturing process compared to traditionalprocess techniques.

The density and mixture of primary fibers as well as secondary fibersmay be varied to suit the particular application. Specifically, in thecase of brake shoes, however, the orientation of the primary fibers maybe in a drum transverse to the drum surface. The fibers are pulledthrough a die having the curve or arc of the desired shoe andselectively cut width-wise. In this application the cut surface does notrepresent the friction surface. A secondary preparation step, such asgrinding, may be performed to attain the desired surface. This is alsotrue for various pad and clutch applicators as described herein.

While brake pads are illustrated in the process, it is apparent thatclutch friction units and brake shoe linings as well as abrasivefriction discs may also be manufactured by this process. The die is setto shape one peripheral surface or outline of the emerging articles andcan include annular shapes. Otherwise, the die can be set to provide atleast one dimension of the article to be manufactured. In the case ofpads for disc brakes, in one embodiment the fibers are orienteduniformly at an angle preferably normal to the friction surface for thehighest efficiency of manufacture. However, in certain applications, anorientation parallel to the friction surface may be satisfactory or evenpreferred for manufacturing as well as performance.

The shoe linings may be formed by the pultrusion process in the form ofa thin arcuate slab, and the linings cut to width as described abovewith respect to pads. This provides an economical technique forproducing consistently uniform units. However, where orientation of thefibers normal to the friction surface is desired, a rectangular slab maybe cut along an arc to form the curved friction surfaces.

The articles may be cut from the pultruded bar by any suitable means,such as by laser, water or other means. The present method and processprovides a highly efficient manufacturing process for the production ofhigh quality friction units that are asbestos free and/or a controlleduniform composition and quality. The pultrusion process enables rapidproduction and the careful control of fiber density filler and frictionformulation, mixture, and orientation on a continuous basis.

The primary reinforcing fibers 14 for the brake pads or linings arepreferably glass fiber, but the pad may contain other materials andfibers or combinations thereof. In addition, other fibers may be wovenor distributed in with the glass fibers in various selecteddistributions and proportions to alter and or enhance certaincharacteristics. For example, various fibers may be distributed invarious concentrations substantially uniformly throughout the unit foroptimizing various parameters such as inner laminar shear strength,wear, fade, and cooling. The addition of secondary reinforcing fiberscan be accomplished in several ways. Many different fibers or strandsand combinations may be utilized, including but not limited to glass,rock, ceramic, carbon, graphite, aramid, nomex, wool and cotton fibersof other organic and inorganic materials. Various metallic fibers suchas copper and aluminum may also be utilized in various proportions withnon-metallic fibers.

The illustrated preferred process utilizes multiple layered fabricpanels of reinforcing fibers. In some instances additional shearstrength may be required between the layers of reinforcing fibers. Onepreferred method of obtaining sufficient strength is by the method ofneedling as illustrated in FIGS. 4 and 5. This process comprises passingmultiple barbed needles down through the panel of fibers as the panelpasses beneath the needles. As shown, the panel 40 has portions orstrands of fibers 46, referred to herein as downturns, extending downfrom the panel. Similar strands of fiber may also extend upward ifdesired. In a preferred method several layers of the reinforcing panelscome together and thereby co-mingle their respective needled portionsresulting in a joining or stapling the woven panels together. Fibersfrom each panel are forced into adjacent panels resulting in a highstrength mechanical bond between adjacent panels. This improves bondingbetween the layers and inner layer shear strength in the final productand helps to limit distortion caused by the pulling forces ofpultrusion.

An exemplary apparatus for carrying out this needling procedure isillustrated in FIG. 5 and designated generally by the numeral 48. Theapparatus comprises a support 50, which is preferably in the form of agenerally rectangular panel, on which is mounted an array of a pluralityof barbed needles 52. A reciprocating power unit 54 such as a hydraulicor pneumatic cylinder is connected to the support 50 and moving itupward and downward to force the needles through one or more layers orpanel 56 of reinforcing fibers forming upturns and downturns as may bespecifically desired. This array of upturns and downturns tend to tiethe panels together once in contact with each other during processing toimprove the internal or inner laminar shear strength of the finalproduct.

Referring to FIG. 6, an exemplary embodiment of a needle is illustratedand designated generally by the numeral 62. The needle 62 comprises anelongated shank 64 having a mounting end 68 and a pointed end 70. A pairof downturned barbs 72 are formed on a lower portion of the shankpointing in the direction of the needle point. A pair of upturned barbsare formed on the shank: above the down turned barbs and point towardthe mounting end of the needle. The panels of matting may also be formedin any number of other ways such as illustrated in FIGS. 7, 8 and 9.Referring first to FIG. 7, a panel 80 is formed of woven fibers orstrands which cross in the traditional manner. However, pairs of strands82 extending in one direction are woven into single cross strands 84.Illustrated in FIG. 8 is a mat 86 formed of a plurality of bundles offibers 88 (vertically oriented) secured together by stitching 90(extending horizontally). A second panel of these is shown layered at anangle of about forty five degrees. These may be layered in manydifferent angles from a few degrees up to 90 degrees.

FIG. 9 illustrates a braided mat 92 formed by braiding multiple stringsor bundles 94 of fibers. The braiding may be relatively loose or tightas desired. Layers of these and the FIG. 8 mats or panels may also beneedled for further composite reinforcement. In addition the reinforcingof a run of composite units may utilize layers of anyone or combinationsof two or all of these mats or panels of fibers.

Referring to FIG. 10 of the drawing, there is schematically illustratedanother method for carrying out an exemplary series of steps ofproducing products such as friction linings for brakes and clutches inaccordance with the invention. The method is carried out in thesubstantially the same system, designated generally by the numeral 10,as previously described. The system comprises source of reinforcingfiber or fabric such as one or more spools or rolls 12 from which apanel 14 of a plurality of strands of an elongated continuous fiber orarrays of fiber are drawn. The panels or arrays of fibers areimpregnated with a suitable resin such as by being passed throughsuitable injection chamber or wetting bath 16 of a suitable resin suchas a phenolic resin and through a forming die 18 from which a compositepanel 20 emerges. A backing or reinforcing panel 96 of metal or othersuitable substantially rigid material is passed through the system withthe resin impregnated fabric panels and is bonded thereto. The compositefabric panel and resin forms a top layer bonded to the backing panelemerging from the pultrusion apparatus or system. The composite panel 98may them be cut into the appropriate shaped units 100 having a combinedfriction surface 102 and backing surface 104. This forms a unit that maybe used for brake or clutch rotors or other friction devices. Thebacking material may be any suitable material such as solid metal panel,perforated metal panel, metal screen, composites and the like. Thisprocess can eliminate the additional step of bonding.

Reinforcing panel 96 may be made of metal or other suitablesubstantially rigid materials. In the context of the disclosed device, asubstantially rigid material has mechanical properties sufficient toprovide additional stiffness or reinforcement to the device so as toimpede undesirable flexing. Substantially rigid materials, as the termis used herein, have a tensile strength higher than 18,000 lb/in², andin more particular implementations between the range of 18,000 lb/in² to290,000 lb/in². Some examples of substantially rigid materials includecast iron (18,000 lb/in²), and steel, as well as other similar materialswith similar strengths such as but not limited to titanium, aluminum,and metal and non-metal composites. Particular examples which fall inthe middle of the acceptable range include, but are not limited to,drawn annealed steel SAE 4340 (290,000 lb/in²), SAE 1300 steel (100,000lb/in² to 240,000 lb/in²), and titanium alloy 6-4 (130,000 lb/in²).Those of ordinary skill in the art may describe tensile strength nearthe higher end of this range as rigid, in which case the reinforcingpanel 96 would be referred to as a rigid panel or a substantially rigidpanel. If the panel is made of metal or includes a metal or a metalalloy, the panel would be called a rigid metal panel or a substantiallyrigid metal panel.

Additionally, particular implementations of the disclosed device may notinclude a rigid backing panel in addition to the resin impregnatedpanels because the long fiber reinforced polymer (LFRP) composites mayhave similar tensile strength to steel.

One a particular composite unit is formed with an aluminum backing forproducing brake rotors of light weight with a durable friction surface.The rotor may be detachably attached to a hub of an automobile toprovide a reduction in the un-sprung weight of an auto suspension andwheel assembly. In an alternate method the substantially rigid core orpanel may be sandwiched between fabric panels to produce a panel havingopposed friction faces as illustrated in FIG. 11. As illustrated a unit106 having a composite face 108 on one side of a substantially rigidpanel 110 and a composite face 112 on the other side. These units can beused as clutch or brake rotors or other friction devices.

Referring to FIG. 12, there is illustrated an embodiment wherein alaminate brake rotor comprises a central lightweight disc 118 having ahub 120 for detachable attachment to an axle hub of a vehicle. A pair ofcomposite rotor discs 122 and 124 are attachable to the central disc toprovide the friction surface for engagement by brake pads. Thisconstruction enables the use of light weight material such as aluminumfor the central hub 118 to reduce the un-sprung weight of an autosuspension. Aluminum has been found not suitable for traditional brakerotors because it lacks sufficient hardness.

The manufacturing system and process, as illustrated and describedherein, provides for the controlled predetermined orientation of theprimary fibers, as well as the controlled predetermined uniformity anddensity of the primary fibers within the resin matrix. For example, thecomposition of the friction device determines many of itscharacteristics, such as its durability, heat resistance, and frictionresistance. With this process, the primary fibers may be controllablydistributed and oriented uniformly at any suitable angle to the frictionsurface of the brake pad or friction device. Thus, the process andmaterials have the capability of providing superior, predictable andconsistent performance.

Milled or chopped fibers such as glass, ceramic kevlar steel, wool orcotton fibers or other may also be added and introduced into the matrixmaterial so that they are picked up by the primary strands of fibers asthey pass through the resin. The chopped fibers may be in the range offrom 1% to about 5% by weight of the matrix material. The short fibersare preferably in the approximate range of 0.015 inch to about 0.062inch and dispersed somewhat uniformly throughout the matrix. Thisdispersement of milled fibers provides multi-axis mechanicalreinforcement, as well as crack and compression resistance in areas tobe machined for mounting purposes. In this process, milled or choppedfibers may be mixed in the primary resin reservoir, or in thealternative two reservoirs of resin may be used. In one arrangement afirst tank contains a low viscosity resin to enhance the wetting of thefibers (preferably predominately glass fibers) as they are passedthrough. The fibers then pass through a second tank of higher viscosityresin containing many of the fillers and chopped wool, cotton or otherfibers. The chopped fibers preferably make up from about 1% to 5% of thereinforcement fibers. They will be picked up by the primary strands offibers and will generally extend transverse to the primary fibers withproper modification of the handling equipment. Other fibers may also beused in this way. These and the transverse fibers may be used togetheror in the alternative to achieve the desired shear strength.Alternatively a variation of woven or striated layers may utilized toprovide desired changes in mechanical properties as may be required inthe areas to be machined for mounting purposes including the use ofsecondary panels or cure composite metal or other types of material usedas an integral backing or reinforcement to the pultruded composite.

The matrix material may be any suitable resin that is either athermoplastic material or non-thermoplastic material, and it may requirevarious forms of curing. It may be cured, for example, by cooling,heating, or by the use of UV or other radiation or the like. However,the materials must be capable of enabling the forming of the units bythe pultrusion process.

One suitable phenolic resin is available from BP Chemicals under thetrademark “CELLOBOND” and product designation J2041 L. This product isdescribed as a high viscosity phenolic for use in heat cured pultrusion,does not require any catalyst and will provide reasonably fast linespeeds and cure cycles. Another suitable phenolic resin is Borden 429Cavailable from the Borden Company and recently improved variationthereof. These resins may be present in the range of from about 30% toabout 60% and provide enhanced efficiency in production. In some cases,the manufactured unit must be post cured to assure the best performance.For example, it may be baked at about 250-500 degrees Fahrenheit for oneor to several hours. Preheating may also be required for larger crosssectional units. This may be taken care of in any suitable manner, suchas by use of an RF oven or radiant heat system and usually requires lowtemperature from about 80 to 150 degrees Fahrenheit.

Another resin that is preferably added or combined with one of the aboveis resorcinol-modified phenolic resin available under the trademarkRescorciphen developed by INDSPEC Chemical Corporation. This resin ispreferably present in the range of from about 0% to about 20% andpreferably up to about 13.8% by weight. The resin may require theaddition of material such as BYK 9010 in an amount of up to about 2.5%weight to control the viscosity of the mixture. The matrix material willbe formulated to include heat dissipation and/or friction modifiers,such as graphite and/or non-ferrous metallic powders and/or the like.For example, from about one to ten percent by weight of one or morefillers and/or modifiers, such as graphite powder and/or one or morenon-ferrous metallic powders, may be incorporated into the matrixmaterial. Other materials include but are not limited to mineral filler,rubber powder, copper powder, ceramic powder, nut shell flour (such aswalnut or cashew). These may each be in the amount of one percent (1%)to ten percent (10%) and preferably in the amount of 3% to 5% by weight.Nut flour has been found to increase the shear strength of the unit andto enhance the fade characteristics of pads or linings. During braking,heat breaks down the nut shell flour causing nut shell oil to combinechemically with the resin polymer molecule in a process known as chainbranching. Thereby, the polymer becomes stronger and more able towithstand high temperatures that contribute to brake fade. The ceramicpowder is preferably in the form of hollow spheres of about seven to tenmicrons. These have been found to serve as a mechanical lubricant in thepultrusion process and to enhance the hardness and wear characteristicsof the friction units.

A preferred formulation of matrix materials includes a wetting agent inthe amount of about 0.0 to 2.5%, Barytes (BaS04) of about 0.0 to 10%,Copper of about 0.0. to 20%, walnut flour of about 0 to 5.0%, Talc Nytal(CaMgSilicateIH20) of about 0.0 to 5.0%, graphite of about 0.0 to 5.0%,Zinc Oxide (friction enhancer) of about 0.0 to 10%, Aluminum Oxide(friction enhancer) of about 0.0 to 10%, brass (friction enhancer) ofabout 0.0 to 10%, and a mold release agent of about 0.0 to 2.5%.

The following examples are intended to illustrate but not limit theinvention. While these examples are typical of formulations that havebeen found to be satisfactory, other formulations will occur to those ofskill in the art and may be used.

Example 1

A suitable test sample of the product was produced having thecomposition of a wetting agent of about 0.035%, Barytes (BaS04) of about5.5%, Copper of about 6.9%, walnut flour of about 2.8%, Talc Nytal(CaMgSilicatelH20) of about 2.8%, graphite of about 3.5%, Zinc Oxide(friction enhancer) of about 4.1%, Aluminum Oxide (friction enhancer) ofabout 4.1% and Axel 1850 (mold release) of about 0.7%. The final producthad about 46.0 wt % glass, about 30.30 wt % filler and about 33.7 wt %resin. The glass was PPG E type phenolic sized woven fabric.

Example 2

Raw Material Weight Percent Phenolic Resin 12.66 Barium Sulfate 15.19Potassium Titanate 12.66 Kevlar 2.53 Calcium Fluoride 5.06 AntimonyTrisulfid 2.53 Zircon 2.53 Aluminum Oxide 1.27 Syn Graphite 7.59 Coke 92.53 Cashew Particles 7.59 Rubber 5.06 Calcium Oxide 1.27 Ceramic Fiber3.80 Vermiculite 10.13 Copper 7.59

Example 3

Raw Material Weight Percent Phenolic Resin 10.53 Barium Sulfate 18.42Steel Wool 205 21.05 Kevlar 0.00 Calcium Fluoride 5.26 Zinc Sulfide 2.63Zircon 3.95 Aluminum Oxide 1.32 Syn Graphite 7.89 Coke 9 2.63 CashewParticles 2.63 Rubber 5.26 Calcium Oxide 1.32 Ceramic Fiber 3.95Vermiculite 10.53 Copper 2.63

Example 4

Raw Material Weight Percent Phenolic Resin 8.33 Barium Sulfate 16.67Steel Wool 205 38.86 Iron Sponge 15.63 Interfibe 230 2.08 Zinc Sulfide2.08 Blank 0.00 Aluminum Oxide 0.00 Graphite A 505 6.25 Coke 9 2.08Cashew Particles 2.08 Rubber 4.17 Vermiculite 4.17

The resins may be aqueous based and contain compounds or additives knownas molecular sieves to reduce by containment free by products which maycause excessive voids in the product. Suitable such molecular sievematerials are available as both sodium activated and hydrated chabazitein several mesh sizes. These products absorb gases and water, reducepotential voids or cracks due to gases and vapor. The typical chemicalnames are sodium alumino silicate and calcium alumino silicate. Theseare in powder form and may be added in amounts of from about 1% to about5% by weight of resin. Another additive which has shown to reduce theamount of water vapor formed during the process is barium sulfate(BaS04) commonly referred to as barite.

The resins may also be non-aqueous based which would eliminate or reducethe need for molecular sieves. The resin may also be low condensationresin which produces less water by products.

The fiber to resin matrix may vary from about one part fiber to two partresin, up to about three part fiber to one part resin. A preferred fiberto matrix composition is from about 35% to 75% fiber to 25% to 40% resinor matrix mix. The matrix preferably has from 5% to 10% by weight of oneor more of graphite powder, copper powder, aluminum powder and theaforementioned powders. In addition, aramid pulp and other syntheticfiber pulps may be added or distributed throughout the matrix material.Other materials such as 3 formulation sheets can be added as required.

Certain thermoplastic materials may be desirable for other specificapplications. The thermoplastic material may, for example, be a suitablepolyester and may also have components such as powders of graphite orother material to aid in friction control and the dissipation of heat.For example, a one to about ten percent by weight of graphite powderuniformly distributed throughout the thermoplastic material aids in thedissipation of heat. Alternate compositions may include small amounts ofother materials, such as non-ferrous metallic powders, such as copper,aluminum or the like. For example, a one to ten percent by weight copperpowder may also be utilized to enhance the dissipation of heat. Thus,the composition must be compatible with the pultrusion process and atthe same time provide satisfactory friction units.

I have discovered that various proportions and compositions of materialscan affect the pultrusion process as well as the performancecharacteristics of the brake pad and lining units. For example, manytest samples with many ranges of examples of compositions have beenconstructed and tested in order to optimize friction units. In recenttests one of the most suitable formulation was found to be wetting agentabout 0.035%, BaS04 about 5.5%, Copper about 6.9%, walnut flour about2.8%, Talc Nytal (CaMgSilicatelH20) about 2.8%, graphite about 3.5%,Zinc Oxide (friction enhancer) about 4.1%, Aluminum Oxide (frictionenhancer) about 4.1% and mold release agent about 0.7%. The finalproduct had about 46.0 wt % glass, about 30.30 wt % filler and about33.7 wt % resin. The fiberglass was PPG “E” type with phenoliccompatible sizing woven into fabric.

While I have illustrated and described my invention by means of specificembodiments, it is to be understood that numerous changes andmodifications may be made therein without departing from the spirit andthe scope of the invention as shown in the appended claims.

The invention claimed is:
 1. A continuous process for manufacturingcomposite friction units comprising: selecting a panel of substantiallyuniform array of predominately glass strands of primary reinforcingfibers, the array of fibers bound together by a process selected fromthe group consisting of weaving, braiding and stitching, the reinforcingfibers making up about 35% to about 75% by weight of said friction unit;wetting said array of primary reinforcing fibers with a phenolic resinmaterial comprising a wet mixture of friction modifiers including about5.8% by weight of graphite powder, about 3 to 5% by weight of nut shellflour, about 0.044% wetting agent, about 5% barite, about 3% talc, about1.9% aluminum oxide and about 0.7% mold release agent; pulling saidwetted array of reinforcing fibers in a predetermined uniformdistribution and orientation through a composite forming die for forminga body having at least a part of a peripheral configuration of saidfriction unit; selecting and pulling a substantially rigid panel throughsaid forming die with said panel of primary reinforcing fibers forming atop layer bonded to the substantially rigid panel emerging from theforming die; solidifying said body by curing said resin, wherein saidbody includes a matrix comprising about 5.8% by weight of graphitepowder, about 3 to 5% by weight of nut shell flour, about 0.044% wettingagent, about 5% barite, about 3% talc, about 1.9% aluminum oxide andabout 0.7% mold release agent; and selectively cutting said body atleast along one path transverse to said strands into a plurality of saidfriction units, thereby forming a plurality of friction units having apredetermined size and configuration and uniform distribution andalignment of fibers throughout.
 2. The process of claim 1 wherein thefriction unit contains about 46.0 wt % glass, about 30.30 wt % fillerand about 33.7 wt % resin.
 3. The process of claim 2 wherein the primaryreinforcing fibers are under tension in said body.
 4. The process ofclaim 1 wherein the primary reinforcing fibers are under tension in saidbody.
 5. The process of claim 1 wherein wetting the array of primaryreinforcing fibers with a phenolic resin material comprises selectingthe array as pre-impregnated fibers.
 6. The process of claim 1 whereinselecting a substantially rigid panel includes selecting a metal panelof aluminum.
 7. The process of claim 1 wherein selecting a substantiallyrigid panel includes selecting a mesh panel.
 8. The process of claim 1wherein selecting a substantially rigid panel includes selecting aperforated panel.